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United States Patent |
5,308,533
|
Hotaling
,   et al.
|
May 3, 1994
|
Aerogel mesh getter
Abstract
A porous light-weight getter which collects particulate and molecular
contaminates that is believed a significant improvement over the prior art
is provided in which a metal mesh matrix is coated with a low-density
porous aerogel. In the prior art bare metal mesh matrices have been
employed as getters, which are subject to ablation from high-velocity
contaminant particles. In the composite getter of the present invention,
the low-density aerogel coating protects the enclosed metal matrix from
ablation and also can attract and hold the incoming high-velocity
particle. On its part, the metal mesh provides reinforcing support to the
aerogel covering and also good thermal conductivity therein so that such
covering can be cooled to the low temperatures that attract such
contaminants. The invention further provides method for manufacture of the
composite getters of the invention. Such composite getters are useful in
decontamination in semiconductor manufacturing processes and storage
thereof and in decontaminating optical systems including a space-based
telescope. In other embodiments, the getter of the invention can be
mounted in air ducts to serve as a filter therefor, can be mounted in a
photocopier for capture of toner fog, can be mounted in areas of
semiconductor manufacturing for collecting contaminates proximate thereto,
can be mounted in operating rooms, cleanrooms, in storage areas for
surgical instruments, in spacecraft and the like for decontamination
thereof.
Inventors:
|
Hotaling; Steven P. (Liverpool, NY);
Dykeman; Deidra A. (Kent, WA)
|
Assignee:
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The United States of America as represented by the Secretary of the Air (Washington, DC)
|
Appl. No.:
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981923 |
Filed:
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November 12, 1992 |
Current U.S. Class: |
252/181.6; 252/181.1; 445/55; 502/233 |
Intern'l Class: |
H01J 017/18 |
Field of Search: |
252/181.1,181.6,315.6
502/233
445/55
|
References Cited
U.S. Patent Documents
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|
3889119 | Jun., 1975 | Whicker et al. | 250/352.
|
4053565 | Oct., 1977 | Krekeler et al. | 423/338.
|
4146497 | Mar., 1979 | Barosi et al. | 252/181.
|
4327065 | Apr., 1982 | von Dardel et al. | 423/338.
|
4444316 | Apr., 1984 | Casberg | 206/524.
|
4619908 | Oct., 1986 | Cheng et al. | 502/214.
|
4630095 | Dec., 1986 | Otsuka et al. | 357/78.
|
4717708 | Jan., 1988 | Cheng et al. | 502/233.
|
4839085 | Jun., 1989 | Sandrock et al. | 252/181.
|
4849378 | Jul., 1989 | Hench et al. | 252/315.
|
4922157 | May., 1990 | Van Engen et al. | 315/248.
|
4977035 | Dec., 1990 | Travis et al. | 428/550.
|
4996002 | Feb., 1991 | Sandrock et al. | 252/181.
|
5004036 | Apr., 1991 | Becker | 164/97.
|
5015411 | May., 1991 | Tom et al. | 252/194.
|
5020583 | Jun., 1991 | Aghajanian et al. | 164/97.
|
Primary Examiner: Stoll; Robert L.
Assistant Examiner: Anthony; Joseph D.
Attorney, Agent or Firm: Singer; Donald J., Stover; Thomas C.
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the
Government for governmental purposes without the payment of any royalty
thereon.
Parent Case Text
This application is a continuation-in-part of application Ser. No.
07/800,817, filed Nov. 29, 1991 now abandoned.
Claims
What is claimed is:
1. A decontamination system comprising a porous, light weight composite
getter which collect particulate and molecular contaminates, said getter
comprising a three-dimensional metal mesh matrix having a porosity of
5-100 pores per inch, said metal mesh matrix being completely coated on
the exterior surfaces thereof with a low-density porous aerogel having a
density of 1-500 mg/cc.
2. The getter of claim 1 which is additionally saturated and coated through
the interior to the exterior surfaces thereof with said low-density porous
aerogel.
3. The getter of claim 1 wherein said aerogel is silica aerogel.
4. The getter of claim 1 wherein said aerogel is of organic or inorganic
compounds.
5. The getter of claim 1 wherein a component of said aerogel is selected
from the group consisting of resorcinol formaldehyde, melamine
formaldehyde, CaF, SiC and Be.
6. The getter of claim 1 having means for cooling said matrix and thus said
getter.
7. The getter of claim 1 wherein said mesh is of aluminum alloy.
8. The getter of claim 1 wherein said aerogel has a density of 3-30 mg/cc
and has a variable compliance tensor.
9. The getter of claim 1 having an annular shape and mountable in an
optical instrument.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lightweight getter for contaminants,
particularly an aerogel mesh getter therefor.
2. The Prior Art
Optical sensors in space-based astronomical observatories and other
observation satellites are often required to detect low-radiance objects
against relatively bright backgrounds such as the Earth and the sum. This
requires that the optical system have a high out-of-field-of-view
rejection capability and thus low scatter optical surfaces (mirrors and
lenses). Launch, deployment and satellite operations such as gimbal
motions create vibration-induced contaminants which have a high
probability of becoming attached to optical surfaces or accumulating in
the sensor's field of view. Propulsion effluents, nonmetatic material
outgasing and the natural space environment also produce contaminants that
can deposit onto surfaces sensitive thereto such as lenses, mirrors and
solar collectors.
To alleviate the above surface contamination problem, certain devices have
been developed which direct a spray, jet or beam at a surface to dislodge
the contaminant particles therefrom. That is, e.g. a gas-solid snow
mixture spray or ion beams are applied to remove contaminants from the
optical surfaces. However, once removed from such surface, these species
must be collected to prevent their re-deposition on an optical surface
and/or their floating in the field of view of an optical instrument.
In the prior art, collectors known as "getters" have been employed for the
purpose of collection or capture of the above contaminants. These prior
art getters have taken the form of one or more layers of metal mesh,
charged plates and charged dielectric plates (electrets). However the
metal mesh device, e.g., of aluminum alloy, are brittle and have
desorption rates and ablation tendencies. The charged plates require
kilovolts of charge which is unacceptable for a satellite due to, e.g.
arcing problems in space. The charged dielectric plates have capture radii
too low to be useful in practice.
Further, high performance optical and micro electronic components have ever
tightening contamination specifications placed upon them. Contamination is
now seen as a major reason for the degradation of space based optical
systems and failure of high density integrated circuits used throughout
industrial and military systems. Contamination is currently controlled by
the use of cleanrooms, process monitors and manual cleaning techniques
which include solvent wipes, strippable coatings, wet-dry processes,
ultrasonics and air purges. The major disadvantages of these techniques
and their inability to remove submicron particles and the potential of
leaving molecular residues on the cleaned surfaces. Some of these cleaning
techniques can be damaging to delicate surfaces and/or have toxic waste
products; for, e.g. biomedical applications such as virology research
laboratories.
To address the above contaminant problem, certain contamination removal and
collection techniques have been attempted to the prior art. However, some
of these removal techniques create a flux of removed contaminants which
can then re-deposit on clean surfaces or be ejected into the environment.
Current collection devices, such as filters, charged metal plates and
screens and charged dielectrics have collection efficiencies and capture
radii incommensurate with the new nano-scale semiconductor devices,
optical systems and biomedical cleanliness requirements.
Accordingly, there is a need and market for a contaminant getter that is
effective and otherwise obviates the above prior art shortcomings.
There has now been discovered a lightweight contaminant getter that
collects and holds particulate and molecular contaminants without the
above-noted high voltage and ablation problems.
SUMMARY OF THE INVENTION
Broadly, the present invention provides a porous lightweight getter which
collects particulate and molecular components comprising, a metal mesh
matrix and a low-density, porous, aerogel coated on said matrix.
The aerogel collects and contains the above contaminants while the metal
mesh provides support for such aerogel and a thermally conductive path by
which such getter can be maintained at a desired temperature for
collection purposes.
Also provided is a method for forming a composite getter which collects and
holds contaminants comprising covering a metal mesh matrix with an
aerogel.
Further provided is a method for preparing a lightweight getter which
collects contaminants comprising condensing an aerogel precursor oil, e.g.
a silica oil onto a metal mesh substrate, catalyzing said oil to form a
gel and extracting solvent from said gel to dry same to a silica aerogel,
to form a getter with a porous low-density aerogel covering on a metal
mesh matrix.
By "low density" aerogel, as used herein, is meant a) aerogel having a
density of from 1 to 10 mg/cc (ULD aerogel) and b) aerogel having a
density of from 10 to 500 mg/cc (LD aerogel).
By "covering" the metal mesh matrix, as used herein, is meant coating or
encapsulating such matrix with an aerogel.
By "coating" such matrix is meant applying a surface aerogel layer thereon,
e.g. per FIG. 5, hereof.
By "encapsulating" such matrix is meant applying said aerogel throughout
and on such matrix, e.g. per FIG. 6 hereof.
By "AMCC" as used herein, is meant Aerogel Mesh Contamination Collector of
the invention. It includes a stand alone device which acts as a "flypaper"
type collector. The AMCC can have arbitrary geometric shapes and
topological and morphological natures depending on function.
By "AMCC/CRS" as used herein, is meant the above AMCC in a configuration
with a Contamination Removal System, e.g. a solid/gas jet spray or ion
cleaner.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will become more apparent from the following detailed
specification and drawings in which;
FIG. 1 is a perspective view of an optical instrument which houses a
collector or getter either of the prior art or of the present invention;
FIG. 2 is a fragmentary sectional elevation view schematic of a contaminant
dislodging apparatus for a substrate;
FIG. 3 is a plan view of mesh sections of getters of the prior art;
FIG. 4 is a plan view of a section of a contaminant getter according to the
present invention which can be employed in the optical instrument shown in
FIG. 1;
FIG. 5 is a perspective view of a composite getter according to the present
invention;
FIG. 6 is a perspective view of another composite getter embodying the
present invention;
FIG. 7 is a sectional elevation, schematic view of a decontaminant filter
system embodiment of the invention;
FIG. 8 is a sectional elevation schematic view of another decontaminant
filter system embodiment of the invention;
FIG. 9 is an isometric schematic view of another composite getter
decontamination system embodiment of the invention;
FIG. 10 is a sectional elevation schematic view of yet another composite
getter decontamination system embodiment of the invention;
FIG. 11 is a perspective schematic view of still another composite getter
decontamination system embodiment of the invention and
FIG. 12 is a perspective schematic view of a contaminate removal and
composite getter, decontamination system embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring in more detail to the drawings, a space-based telescope 10 having
a barrel 12, cover 14, primary optical component, e.g. mirror 16, having
cleaning jets 20, and annular collector or getter 22, are mounted in the
telescope barrel 12, as shown in FIG. 1. This telescope system is known in
the prior art.
As shown in FIG. 2, the mirror 16 of the above telescope employs cleaning
nozzles or jets 20, which direct a solid/gas jet spray of snowflakes 24
against contaminant particles 26, to dislodge them from the surface of
such mirror 16, as shown in FIG. 2. The so-dislodged particles 26 are then
supposed to be captured by the getter 22 of FIG. 1.
Prior art getters which have been discussed above, have included aluminum
alloy mesh sections such as mesh section 30, having ten pores per inch,
mesh section 32, having 20 pores per inch and mesh section 34, having 40
pores per inch, as shown in FIG. 3.
As noted previously, the above aluminum alloy mesh getters are brittle, are
subject to desorption of the captured particles and are subject to
ablation upon collision therewith by the so-dislodged particles. That is,
as shown in FIG. 3, particle 31, upon collision with getter mesh section
34 causes ablation and launching of two aluminum mesh particles 33 and 35
as shown. Thus the capture and retention rate of contaminant particle (and
molecules) by prior art getters is unacceptably low and many of these
non-captured particles can redeposit on optical components or float in the
optical sensor's field of view.
To alleviate the above problems, the getter of the present invention is
provided. That is, a low-density, porous material is coated onto a metal
mesh section to provide an improved contaminant getter according to the
invention. For example, as shown in FIG. 4, metal mesh section 40 has an
ultra-low density (ULD) silica aerogel condensed thereon to provide an
effective and improved getter according to the present invention, which
attracts and holds contaminant particles or molecules, thus enhancing the
contaminant cleaning process, e.g. in an optical telescope such as shown
in FIG. 1.
In FIG. 1 is also shown an electron gun 18 which (by electron beam 19) is
used to sputter molecular contaminants from optical surfaces. Also, the
jet spray nozzles 20 direct snowflakes within a gas stream at the
substrate 16, per FIG. 2, to remove contaminate particles. As the
contaminants are removed from the optical surface, they are attracted to
and held by the getter 22 of the invention, as shown in FIG. 2.
Also, as shown in FIG. 1, a coolant line 25 (for, e.g. liquid N.sub.2)
divides into cooling branch lines 27 and 29, as shown in FIG. 1. Coolant
line 29 connects with and cools primary mirror 16 while coolant branch
line 27 connects with and cools getter 22 as shown in FIG. 1 and indicated
in FIGS. 2, 5 and 6. The getter may also be cooled using a cryocooler by
means known in the art.
The metal mesh segment of the invention is shown in two embodiments in
FIGS. 5 and 6. Thus metal mesh block 44 has coolant branch line 27 running
therethrough and is coated on its exterior surfaces with layers of silica
aerogel, i.e. layers 46, 48 and 50 as shown in FIG. 5.
Alternatively another composite getter embodiment of the invention is shown
in FIG. 6 wherein the metal mesh block 52 (which has coolant feed line 27
running therethrough) is encapsulated or coated throughout as well as on
the exterior surfaces thereof) with low density silica aerogel 54, as
shown in FIG. 6.
In either embodiment a getter surface coated with low density (including
ULD) aerogel is presented to an oncoming particle which can collide with
and imbed itself into the aerogel covering at the surface of the getter or
below the surface thereof.
As noted above, the aerogel covering protects the metal mesh core or
substrate thereunder from ablation upon impact by a fast-moving
contaminant particle or molecule. At the same time the metal mesh core,
e.g. mesh 44 of FIG. 5 or mesh 52 of FIG. 6, provides good thermal
conductivity to the coolant feed line 27 and thus enable the fast cooling
of the aerogel coating of the respective composite getter, the better to
attract contaminants to the getter.
Thus the getter of the present invention is a fusion of a suitable metal
mesh with a low density cellular foam, e.g. a silica aerogel having a
preferred density of 3-30 mg/cc.
The components of the getter of the invention e.g. shown in FIGS. 4 and 6
complement each other in that the aerogel is flexible, hydrophilic, porous
and has a high compliance tensor in low temperature environments. Aerogel
also coats and protects the metal mesh from ablation upon particle impact,
and attracts and holds such contaminant and prevents its redeposition on
an optical surface. On its part, the metal mesh provides a reinforcing
element to the aerogel covering and such mesh provides good thermal
conductivity within such covering. This is important because a cold getter
better attracts contaminants and the metal mesh's thermal conductivity
serves to maintain the aerogel covering as cool as desired, e.g. in an
optical instrument for attraction of contaminant particles or molecules.
A word about the method for preparing ULD silica aerogel employed in the
getter of the present invention. While such method is not part of the
present invention, the end product is and accordingly such method is
briefly discussed. This is because the ULD aerogel employed in the getter
of the present invention is different from more conventional aerogels
which have greater density and thus greater weight, lower porosity, and
lower particle absorption capability.
Conventional silica aerogel employs the hydrolysis and condensation of
tetraethoxysilane (TEOS) and/or tetramethoxysilane (TMOS) to produce gels
which are then supercritically extracted to a low-density silicon glass
network. This single-step solgel process has been used for several years
in producing materials with densities ranging from 20 to 1100 mg/cc. This
method is suitable for preparing LD aerogels employed in the present
invention However, such method requires high temperatures, e.g.
400.degree. C. and pressures, e.g. 300 bars and certain precautions may be
required.
The present invention employs an aerogel preferably made by a two-step
extraction process. The two-step process differs from a conventional
solgel process in that it generally proceeds at lower temperatures and
pressures than the above one-step process and instead of requiring an
extremely dilute solution to gel as in the single-step reaction, a
partially hydrolyzed, partially condensed polysilicate mixture is prepared
from which the alcohol is replaced as the solvent and then this
non-alcoholic solvent is supercritically extracted.
That is, the solvent replacement technique employs liquid carbon dioxide,
CO.sub.2, to purge the system of the alcohols and then supercritically
extracts the replacement solvent, i.e. heats the system to a relatively
low 40.degree. C. (and e.g. 40 bars pressure) to drive off the CO.sub.2.
This leaves a very low density silicon dioxide network or aerogel, with
densities ranging from 1-900 mg/cc.
In a more specific example, an aerogel getter of the invention is
fabricated using the above technology by first preparing a condensed
silica oil by reacting TMOS with a sub-stoichiometric amount of water in
methanol, under acidic conditions, with the following molar ratios:
1 TMOS:1.3 H.sub.2 O:2.4 MEOH:10 HC1.
This mixture is then distilled, removing much of the methanol and leaving
the silica oil (which includes the TMOS). The oil is then hydrolyzed:
1 TMOS:4.0 H.sub.2 O
This reaction is done in a pyrex glass mold in the presence of a
non-alcoholic basic diluent (NH.sub.4 OH). Also present in the glass mold
is a metal mesh and a catalyst (referenced below). Gel times vary from
12-72 hours. The silica aerogel is obtained from this "alcogel" by using
liquid carbon dioxide to purge the alcogel of alcohol and replace it with
such liquid carbon dioxide (which keeps the aerogel pores open).
Thereafter heat is applied to raise the temperature of such aerogel to
about 40.degree. C., to apply super-critical triple point extraction
(CO.sub.2 phase diagram) to drive off such replacement solvent in the
autoclave. The temperature is ramped (up to about 40.degree. C.) while
pressure is controlled and when finished, the autoclave (and the dried
porous aerogel) is purged with dry nitrogen. The aerogel-coated mesh or
getter of the invention is then removed from the mold for testing, storage
or for use in decontamination of optics.
For more information on the above two-step extraction process or solvent
replacement technique, in preparing aerogels, see an article by Laurence
Hrubish and Thomas Tillotson in a book entitled "Better Ceramics through
Chemistry Part IV," Materials Research Society, MRS Press, Pittsburgh,,
Pa., 1991, which article is incorporated herein by reference.
In an example of fabricating a composite getter, according to the present
invention, an aluminum alloy mesh at e.g. 10 pores per inch, is placed in
a pyrex glass mold in an autoclave and covered with a solution of TMOS and
undergoes the above-mentioned hydrolysis and condensation reactions in the
presence of a catalyst as more fully described in the above-cited
publication. A gel forms around the wire mesh and the gel undergoes a
two-step solvent extraction process in which methanol is replaced by
liquid carbon dioxide as an intermediate solvent as noted above. The
liquid carbon dioxide is then supercritically extracted using the
triple-point (phase diagram) drying technique. The pH and solvent/solute
mixing ratios are set to achieve aerogel densities on the order of 3-30
mg/cc. The autoclave is then purged with dry nitrogen as discussed above
and the composite getter of the invention obtained.
As indicated above, the aerogel employed in the getter of the invention is
suitably a silica aerogel which has been extracted to a low-density silica
porous glass network. However other low density aerogels can be employed
within the scope of the invention, including inorganics from the Periodic
Table of The Elements, eg. aerogels of SiC, CaF or Be and including
organics, eg, aerogels of resorcinol-formaldehyde and of
melamine-formaldehyde.
The aerogel employed in the getter of the present invention has a density
ranging from 1-900 mg/cc and preferably from 3-30 mg/cc.
The metal mesh components used in the composite getter of the present
invention can be of aluminum alloy mesh or other metal mesh and can have
pore sizes ranging from 5-100 pores per inch. Such metal mesh can be, e.g.
coated with aerogel, per the invention, to form a coating thereon, e.g. of
30 to 500 microns thick.
The getter of the invention can be made in various shapes, e.g. annular as
shown in FIG. 1 or other suitable shape and can be employed in
decontamination of optical or other systems, on land, sea, in the air and
preferably in space applications.
The composite getter of invention is suitable for use in 1) contamination
prevention of small and large optical systems including telescopes,
interplanetary and solar explorers and space stations, 2) contamination
prevention for ground-based systems and components whether in clean rooms,
test chambers, storage, transportation or operation, as well as 3) in
semiconductor processing operations.
The composite getter of the invention serves also to collect and contain
particulate and molecular contaminants in order to prevent their
deposition onto sensitive optical surfaces during testing, storage,
transportation, launch, deployment and operation of sensor systems. The
physics of low density aerogels compensates for the shortcomings of metal
mesh getters and is believed to represent a significant advance in getter
design.
The composite getter of the invention is coated with a low-density, porous
aerogel that, as noted above, has a high-compliance tensor in
low-temperature environments. That is, the aerogel coating has a somewhat
flexible surface so that upon being struck by a high-velocity particle,
the surface will tend to liquefy or soften and admit the particle and then
hold it. In the prior art such high-velocity particle on impact, e.g. with
a metal mesh getter, fractures and ablates the surface thereof, causing
the formation of additional contaminant particles in the system.
In addition to the space-based application described above, the aerogel
getter of the invention can be used with ground-based space simulation
chambers during vacuum and vacuum cryogenic optical testing. It may also
be placed inside of optical storage and transportation vessels as well as
at semiconductor manufacturing and processing locations, to maintain
required cleanliness levels.
In further embodiments of the invention, the AMCC embodying the invention,
can be employed as air filters in, e.g. hospital rooms, as collectors and
filters for environments in which virus and disease molecules can become
airborne threats as aerosols. Such filters, which can also serve molecular
sieves, are applicable to HIV hospital care units and biomedical research
laboratories.
Thus per FIG. 7, in an air duct system 60 in, e.g. an operating room or a
medical lab, circulating fan 62 pulls aerosol laden air into such duct 60
and through the AMCC 66 of the invention and removes, filters out or
entraps, e.g. virus and disease molecules or other contaminants,
outputting cleaner air 68, as shown in FIG. 7.
Such embodiment of the invention can find use in other applications. These
applications include use in electronics medical equipment fan filters. In
these high probability of hazardous aerosol type environments, electronic
instrumentation, most of which contains small cooling fans, creates air
currents. Airborne contaminants are swept up on air currents created by
these fans, to be scattered. Aerogel mesh filters (or AMCCs) for these
fans, would not only act as molecular sieves but also chemically bond,
e.g. to viral species.
In another embodiment, a gas purifying and collection system 7, employing
an AMCC sieve of the invention, is shown in FIG. 8. Here a bottle 72 of
semi-purified gas, e.g. silane gas having silica particles therein, feeds
through valve 74, pipeline 76, AMCC 78 and valve 80 into storage in a
vacuum bottle 82, as shown in FIG. 8. Here the aerogel mesh filter of the
invention (AMCC) collects the solid silica particles, and/or molecules,
passing a purified silane gas into the vacuum bottle 82, as indicated in
FIG. 8.
Thus the system of FIG. 8 can be employed for providing high quality gas
i.e. SiH.sub.4, which gas is filtered by the AMCC of the invention, e.g.
to remove SiO.sub.x particles and water molecules (which can condense in
the gas line 76 of FIG. 8) and obtain a purified silane gas in the vacuum
chamber 82 for use in fabricating silica thin films and semiconductors in
a high purity environment.
Such purifier systems embodiment of the invention can be employed
biotechnically to pass aerosols of micro-organisms through such
decontamination system 70 and through the AMCC 78 which, dependent upon
pore size (of the aerogel mesh filter), will pass smaller molecules or
micro-organisms and prevent larger molecules or micro-organisms from
entering the vacuum chamber 82, as indicated in FIG. 8 hereof.
Accordingly, this embodiment of the invention provides a biotechnology
filter for micro-organism (or other particle) sizing within the scope of
the invention.
The AMCC of the invention also finds application in an IC nano-fabrication
or microfabrication mask aligner and UV exposer. In this apparatus, a high
precision microcircuit is lithographed by large scale mechanical motion in
a robotic system. IC features at submicron dimensions are created. At the
same time, the robotic motion of the system creates aerosols of
particulate and molecular species at submicron spatial dimension (as a
colloid's inertia is characterized by Brownian motion). Also, the UV light
employed in such apparatus can photopolymerize there aerosol particles.
Accordingly, several strategically placed AMCCs are required herein to
obviate the above micro and nano contamination threat.
Thus with reference to FIG. 9, mask fabrication apparatus 86 has stage 88
which supports a photographic plate 90 under mask 92, in turn under UV
lamp 94, as shown in FIG. 9. On such stage 88, 3 AMCCs 95, 96 and 97 are
positioned around the plate 90, mask 92 and UV lamp 94, as shown in FIG.
9. As always, the AMCCs are maintained at low temperature to attract
decontaminants, including aerosols of particulate and molecular species
emanating from the motion of the robotic system (not shown).
In another embodiment, in offices and print shops, the AMCC embodying the
invention is advantageously employed. Thus in photocopiers, FAX machines
and computer printers, the black carbon-base toner is a constant source of
airbone contamination which collects on the interior surfaces of these
machines. The insertion of one or more embodiments of the AMCC of the
invention, in various suitable shapes, inside these machines, provides a
means to collect, e.g. toner fog (carbon or dried paint particles in air),
serves to prolong copier use time between failure and makes for cleaner
air quality in the room or office housing these machines.
The AMCC embodying the invention also finds needed use as on-chip getters.
That is, in semiconductors today, the microchip offgases and conventional
silica gel getters, collect and contain contaminants (e.g. water) up to
approximately 150.degree. mostly collected by the getter 122 therein, the
decontaminated or less contaminated spray 127, exiting the waste container
120 as shown or indicated in FIG. 12.
The above contaminant removal and collection system embodiment of the
invention, can be employed for cleaning of wafers and circuits thereof,
the wafer holder, the process chamber and vacuum chuck cleaning as well.
Further applications of the above contaminant removal and collection
system include the cleaning of:
a) semiconductor wafers prior to and following processing,
b) deposition chambers and all equipment used for semiconductor processing,
c) any coating pre-processing operations, such as painting preparations
where particulates in the air as well as the environment, can cause
significant part reject rates and
d) hospital operating rooms in which surgical implements, surfaces (e.g.
table tops) and instrumentation may be cleaned down to the micron sized
contaminant level.
Other use seen for the getter embodying the invention include:
a) underground waste dumps. Here radioactive waste can react with the
alkalai halides. The getter of the invention can be employed to collect
and contain these species for further study.
b) hazardous waste incinerators and smoke stacks: the getter of the
invention can be used as a collector in various stages of incinerators and
smoke stacks and species collected for laboratory study and
c) in various mechanical systems with moving parts wherein a contamination
free environment is required: for example, a cryocooler (used in
spacecraft systems) in which moving parts create contaminants which
eventually degrade performance. A small aerogel mesh getter of the
invention can alleviate this contamination source and extend the mission
lifetime of the spacecraft and tactical sensor systems using cryocoolers.
In an operating room or cleanroom, or in a room containing paint vapors,
one can advantageously use the fan filter assembly of FIG. 7 and the jet
spray-waste container system of FIG. 12, for thorough decontamination
thereof.
Thus in the embodiments discussed above, the effectiveness of Applicants'
getter embodiments are shown, e.g. for decontaminating metal, glass,
ceramic, semiconductor and polymer substrates. This system applies to both
cleanroom and cryogenic-vacuum conditions such as spacecraft environments.
In addition the AMCC or getter can be used in a stand alone configuration
in which it collects contaminants in "flypaper" fashion or as a gas/air
filtration system. The getter of the invention is believed an advance in
the state of the art getter technology because it can collect and contain
both molecular and particulate contaminants over a wide temperature range.
Additionally, the AMCC/CRS embodiments of the invention can remove as well
as collect and contain contaminants over a wide temperature range, in
vacuum or ambient conditions.
Thus the above getter embodiments of the invention find application in,
e.g. semiconductor processing, biomedical laboratories, hospital operating
rooms, computers and electronic equipment, office and printing equipment,
hazardous waste handling systems, gas filtration systems, semiconductor
devices (on-chip in situ getters) and spacecraft systems.
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